Embodiments according to the invention relate to sheet handling plants and in particular to a method and an apparatus for determining a subgroup of a group of sheets in sheet stream.
Sheet handling plants process, for example, paper rolls having documents printed thereon. Such printed paper rolls will in the following also be referred to as sheet stream. A sheet stream includes groups of associated sheets, which are associated, for example, as regards to content. During processing the sheet stream in the sheet handling plant, the sheets are singularized and the sheets are collected in a group.
Paper handling systems are mainly applied by large companies, banks, insurance companies, service companies, etc. In these companies, the paper handling systems serve to process large amounts of paper, such as invoices, reminders, accounts, insurance policies or checks. In many cases, individual papers to be handled by such paper handling systems are generated by high-speed printers printing letters, forms, etc. on a web. This web is typically provided from a large supply roll to the printer and supplied to the paper handling system after printing.
FIGS. 14 and 15 show a schematic representation of a sheet handling plant 1500. The sheet handling plant 1500 in FIG. 14 comprises a separating device 1510, a merger 1520, a stop location 1530, a first collecting station 1540 and a second collecting station 1550. The sheets of the sheet stream 1502 are singularized by the separating device 1510, also called cutting device or cutting machine. Then, the sheets are placed on top of each other or superimposed by the merger 1520 and transferred to the stop location 1530. From there, the sheets reach the first collecting station 1540, where all sheets of a subgroup are collected and output to the second collecting station 1540. In the second collecting station 1550, for example, all subgroups of a group are collected and the whole group is output.
A group of sheets can, for example, be invoices, reminders, accounts, insurance policies or checks belonging to the same person. Then, a subgroup of sheets comprises a portion of the sheets of the group.
The merger 1520 or the stop location 1530 can be implemented to retain one or several sheets of a row that do not belong to the same subgroup as the first sheet of the row.
The sheet handling plant shown in FIG. 15 essentially corresponds to the sheet handling station shown in FIG. 14, however, instead of the second collecting station, it comprises a folding unit 1560 followed by two transport modules 1570, 1580. The folding unit 1560 can fold the sheets of a group or subgroup and provide them to an inserter for inserting into an envelope. The completely filled envelopes can then be collected at the depositing location.
FIG. 16 shows a schematic illustration of part of a sheet handling plant 1600. In addition to a separating device 1510, a merger 1520 and a stop location 1530, a supply device 1610 is shown. The supply device 1610 can, for example, provide the sheet stream 1502 in the form of an endless web from a roll 1612 to the separating device.
FIG. 17 shows a further schematic illustration of a sheet handling plant 1700. The structure of the sheet handling plant 1700 essentially corresponds to the plant of FIG. 14. However, the merger 1520 is based on a different design principle (superimposing or diverting the sheets) and a transport module 1710 exists between the merger 1520 and the separating device 1510.
Further separating devices are described, for example in EP 1741653 A1 and WO 2006/034596 A1. EP 1741653 A1 shows, for example, a cutting plant for singularizing sheets of a sheet stream. Here, the sheet stream is first separated longitudinal to the main processing direction and the resulting webs are superimposed such that the sheets that have been adjacent to each other before separation will be on top of each other. Then, a separation perpendicular to the main processing direction follows.
WO 2006/034596 shows a similar paper separation means, wherein the web with the printed sheet stream is again first cut longitudinal to the main processing direction and then, after placing the sheets previously adjacent to each other on top of each other singularized perpendicular to the main processing direction.
A problem with such paper or sheet handling plants is that specific parts of such paper processing plants cannot process any number of sheets simultaneously. For example, a folding unit can only process a specific number of sheets simultaneously. Since a group in the sheet stream, however, can be of any size, the same frequently includes more sheets than the maximum number of simultaneously processable sheets. Therefore, such groups have to be divided into subgroups. In known systems, for example, subgroups are formed with the same number of sheets. Thereby, it frequently happens that after singularizing, individual sheets will be processed in the following operating steps. When the groups in the sheet stream have a disadvantageous position and length, this can result in a significantly worse throughput of the paper handling plant than theoretically possible. A subgroup is therefore formed, for example, after four sheets, independent of the group end and of paired or unpaired sheet sequences. This results, for example, in many single sheet entries into the collecting station.
In a specific example, for dividing large groups of sheets, normally, the subgroups are already formed in the merger, which are collected in the first of two collecting stations and subsequently collected in the second collecting station to form the complete group. For this, a fixed number of sheets per intermediate output are predetermined in the merger. One bit is defined, which is set by the merger at the subgroup end, such that the collecting station, when this bit arrives, also detects the subgroup end and hence starts an intermediate output. Also, by reading after a predetermined adjustable number of sheets, a subgroup end bit can be generated. A disadvantage of this method is that the subgroup formation, depending on the group distribution on the incoming paper stream or sheet stream can result, for example, in two unpaired outputs, although the two outputs belong to the same group, but to different subgroups. Additionally, a subgroup consisting of only one input into the collecting station is also disadvantageous for the cycle performance or throughput, since this input immediately causes an output of the collecting station. However, this is only possible in the collecting station when the output drive is again ready for output from the previous cycle.
In this regard, FIG. 2 shows a schematic illustration of a sheet stream 200 with a constant number of sheets 210 in a subgroup. The sheet stream is shown once prior to singularizing and once after singularizing and superimposing the sheets of a row. A subgroup comprises, for example, exactly four sheets. In this example, the sheet stream 200 has two adjacent sheets 210 each in one row and a main processing direction 230 marked by the arrow. The figure shows a paired start of the subgroup on sheet 1 and a subgroup end 220 on sheet 4. FIG. 2 can, for example, represent the paper stream in the cutting machine.
A group of five sheets having an unpaired start is significantly worse as regard to cycle performance or throughput. In this regard, FIG. 3 shows a schematic illustration of a sheet stream 300 having a constant number of sheets 210 in a subgroup. In this example, first, an entry of a single sheet in a first operating cycle, followed by two sheets in a second operating cycle and again a single sheet in a third operating cycle into the collecting station of a sheet handling plant would result. Then, the subgroup end 220 would be reached and the subgroup would be output by the collecting station. Then, in a further operating cycle, an entry of a further single sheet into the collecting station would take place and the same would be output individually again by the collecting station, since the group end 310 is reached. Thus, four operating cycles would be necessitated for processing five sheets.
FIG. 4 shows a schematic illustration of further examples 400 of a sheet stream having a constant number of sheets in a subgroup. Here, it can be seen that depending on the number of sheets in a group and a paired or unpaired start, the cycle performance rises or falls.
A known approach for improving cycle performance or throughput is optimizing the print stream. This means the order in which the groups of sheets are printed on the web is changed. For example, the sheet groups are sorted according to group size.
EP 1770503 A2 and US 2007/0053001 A1 show options for optimizing the print stream prior to printing. This variation has two significant disadvantages. On the one hand, the cycle performance can only be increased when optimization already takes place prior to printing. For webs that are already printed, these methods cannot be applied. On the other hand, optimizing the print stream necessitates high computing power, in particular when the number of groups becomes large.